UW-Madison Insect Diagnostic Lab (Division of Extension / Department of Entomology), P.J. Liesch: Wisconsin is home to approximately 500 species of spiders, and essentially all of these are harmless, beneficial creatures that provide us with an astonishing amount of free pest control*.
This page lists 1 spider.
1 is venomous by official accounts. UW-Madison Insect Diagnostic Lab (Division of Extension / Department of Entomology), P.J. Liesch gives a total of 500; the 1 here are the spiders official sources name one by one.
Not every species: no complete official list of Wisconsin spiders exists, so this page covers the ones state and Extension sources name. How lists are built.
Which spiders can hurt you
Official sources single out these spiders in Wisconsin, in their own words:
Venom: “Black widows and brown recluses are two types of venomous spiders in the United States.” (CDC / NIOSH)
Range: Rare; documented in fewer than 10 counties, mostly east-central counties near Lake Michigan (Door County most), also prairie areas in Crawford, Grant and Sauk counties (UW IDL 2018)
When spiders are active in Wisconsin
Records of spiders in Wisconsin peak in June and August to September. They show when people record spiders, not how many there are (about month bars).
JanFebMarAprMayJunJulAugSepOctNovDec
1,933 records of spiders in Wisconsin by month (GBIF, CC0 and CC BY records).
If you are bitten or stung
Call 911 or Poison Help at 1-800-222-1222 right away. Poison Help connects you to your local poison center, any time of day.
How to report
Rattlesnake sightings: call DNR 1-888-WDNRINFO (1-888-936-7463), or use the DNR Rare Species Observation Form / DNR Wildlife Switchboard ([email protected], 608-267-0866). Threatening wolves or wolf depredation: USDA-Wildlife Services (north 1-800-228-1368, south 1-800-433-0663). Spongy moth outside quarantined counties: 1-800-642-MOTH (6684). Other invasive species: DNR Report invasive species page. Feral pig sightings: DNR reporting form or USDA Wildlife Services (north 800-228-1368, south 800-433-0663). Wisconsin Department of Natural Resources, Bureau of Endangered Resources
Venom labels come only from official sources and link to them; "Not stated" never means harmless. How labels work.
Sources
Wisconsin Animals. Wisconsin Department of Natural Resources. undated page; checked November 3, 2026.
Black Widows: The Hermits of Door County. UW-Madison Insect Diagnostic Lab (Division of Extension / Department of Entomology), P.J. Liesch. May 22, 2018; checked November 3, 2026.Quoted passages (2)
“Wisconsin is home to approximately 500 species of spiders, and essentially all of these are harmless, beneficial creatures that provide us with an astonishing amount of free pest control*.”
“While we’re outside the native range of the dreaded, but horribly misunderstood brown recluse spider (Loxosceles reclusa), Wisconsin is actually home to a native black widow species—the northern black widow (Latrodectus variolus).”
“Black widows and brown recluses are two types of venomous spiders in the United States.”
Common Spiders In and Around Homes (PM 1722 / A2135 / FO-1033-B). University of Wisconsin-Extension with Iowa State University and University of Minnesota Extension (hosted by UW Insect Diagnostic Lab). Revised February 2012; checked November 3, 2026.Quoted passages (1)
“However, dangerous spiders such as the black widow and brown recluse, both very rare in the upper Midwest, require immediate attention and control.”
